Article
Mechanics
Xiongbin Jia, Yong Xu, Hongtao Zheng, Huangwei Zhang
Summary: Two-dimensional simulations were conducted to study the direct initiation of cylindrical detonation in hydrogen/air mixtures with detailed chemistry. The effects of hotspot conditions and mixture composition gradient on detonation initiation were investigated. It was found that detonation initiation failed for low hotspot pressures, while high hotspot pressures led to the critical regime dominating. Detonation was directly initiated from the reactive hotspot, whereas ignition occurred beyond the non-reactive hotspots. Different cell diverging patterns were identified, and cell coalescence was observed when many irregular cells were generated initially.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Engineering, Aerospace
P. V. Kozlov, I. E. Zabelinsky, N. G. Bykova, G. Ya. Gerasimov, V. Yu. Levashov, Yu. V. Tunik
Summary: This paper presents a description of the modernized detonation driven shock tube DDST-M, which simulates the entry of spacecraft into the Earth's atmosphere. The inclusion of a prechamber in the design increases energy efficiency and experiments were conducted to study the radiation characteristics of high temperature air.
Article
Mechanics
S. S-M Lau-Chapdelaine, Q. Xiao, M. Radulescu
Summary: Research investigates large-scale convective mixing through shock reflection experiments and simulations in different gas environments, revealing the effects of Mach number, Reynolds number, and isentropic exponent on forward jetting behavior and Mach stem bifurcation, as well as the large-scale convective mixing induced by Kelvin-Helmholtz instabilities.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Bhavraj S. Thethy, Mohammad Rezay Haghdoost, Rhiannon Kirby, Bonggyun Seo, Maikel Nadolski, Christian Zenker, Michael Oevermann, Rupert Klein, Kilian Oberleithner, Daniel Edgington-Mitchell
Summary: This study investigates shock diffraction through a non-quiescent background medium using both experimental and numerical techniques. The results show that unlike shock diffraction in quiescent media, a spatial distortion of the shock front occurs in the non-quiescent background medium, resulting in a region of constant shock angle. The study finds that the distortion is not due to the geometrical influence of the nozzle, but rather depends on the magnitude of the background flow velocity.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Atomic, Molecular & Chemical
I. E. Zabelinsky, P. Kozlov, Yu Akimov, N. G. Bykova, G. Ya Gerasimov, Yu Tunik, V. Yu Levashov
Summary: An upgraded double-diaphragm shock tube is described in the paper, which uses strong shock waves for detonation initiation to simulate the entry of spacecraft into the Earth's atmosphere at the second cosmic velocity. By optimizing combustion and using hot gas jets through a special perforated disk, the tube achieves gas combustion in the energetically efficient Chapman-Jouguet detonation mode.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Article
Thermodynamics
Caleb White, Humberto Silva, Peter Vorobieff
Summary: The computational simulation of various mixing laws for gaseous equations of state showed discrepancies with nominal experimental data, indicating that none of the equations of state accurately predicted the properties of the shocked mixture. Kinetic molecular theory introduced a parameter that may offer an explanation for these discrepancies, leaving implementation into the equations of state for future work.
JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER
(2021)
Article
Energy & Fuels
Lu Jie, Zhang Hao, Tan Wenhao, Zheng Longxi
Summary: A combined aero-valve was designed and tested to effectively isolate back pressure waves in a valveless pulse detonation combustor within a short axial distance. Experimental and numerical simulation results demonstrated the capability of the combined aero-valve to isolate back pressure waves within a specific firing frequency range.
Article
Energy & Fuels
Yuanyi Liu, John H. S. Lee, Houzhang Tan, Hoi Dick Ng
Summary: This study investigated the impact of wall roughness on detonation velocity, cellular structure, and propagation limits in tubes by using a wire spring to induce roughness. It found that wall roughness increases velocity deficit, enlarges cell size, and makes cell structure more irregular. Contrary to previous studies, wall roughness was shown to narrow the detonation limits.
Article
Engineering, Aerospace
N. N. Smirnov, V. F. Nikitin, L. I. Stamov
Summary: This study conducted a three-dimensional numerical simulation of the reflection and focusing processes of shock waves. Different development scenarios were observed depending on the intensity of the incident shock wave, and the influence of turbulence on the simulation results was discussed. The numerical simulation showed good agreement with experimental data within the critical process parameter range.
AEROSPACE SCIENCE AND TECHNOLOGY
(2022)
Article
Engineering, Aerospace
Jorge Sousa, Elena Collado-Morata, Guillermo Paniagua
Summary: This paper presents a design methodology for turbine stages suitable for supersonic inlet conditions and provides a detailed analysis of optimized turbine geometries. Shock-wave interactions are identified as the main contributors to turbine losses, and optimal pitch-chord ratios and metal angles are calculated for maximizing power extraction.
CHINESE JOURNAL OF AERONAUTICS
(2022)
Article
Mechanics
Eric Won Keun Chang, Wilson Y. K. Chan, Timothy J. McIntyre, Ananthanarayanan Veeraragavan
Summary: In this study, experimental investigations were conducted on hot-wall hypersonic impinging shock interactions in a flight-representative environment. The results showed that with higher wall temperatures and lower unit Reynolds numbers, flow separation size increased. The data did not align well with existing separation correlations due to the stronger shock strength, and instead followed a scaling law based on pressure ratio and wall temperature ratio.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Multidisciplinary Sciences
Meera Chadha
Summary: This study analyzes an intense explosion in dusty gas by using the 2020 Beirut ammonium nitrate explosion as a case study. The energy released by the explosion and the estimated reduction in damage radius in the presence of additional dust particles in the atmosphere are determined. It is found that the specific dust parameters play a crucial role in enhancing decay and reducing pressure in dusty gases.
PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2022)
Article
Mechanics
Michael Groom, Ben Thornber
Summary: The effects of initial conditions on the evolution of the Richtmyer-Meshkov instability (RMI) are analyzed using numerical simulations and compared with experimental results. Various measures of mixing layer width and decay rate of fluctuating kinetic energy are used to explore the effects of initial conditions, and good agreement is found with experimental data. The results demonstrate differences between broadband and narrowband perturbations and emphasize the importance of considering the concentration field when inferring properties based on the velocity field.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Thermodynamics
Neil K. Bourne
Summary: This paper investigates the stress threshold required to fully detonate an explosive. The results suggest that there is a critical stress level, known as the Weak Shock Limit, at which the explosive's response changes. Experiments indicate that in the strong shock region, the explosive's response becomes independent of microstructure and there is a transition in the energetic crystal's electronic state. This hypothesis has implications that can be further tested in experiments.
COMBUSTION AND FLAME
(2022)
Article
Engineering, Mechanical
Desen Hou, Q. M. Li
Summary: This paper investigates the damage boundary of a single-degree-of-freedom (SDOF) structural model under shock environment. The shock environment is characterized by different shock-waveforms, and the upper and lower damage bounds on the shock response spectrum graph are proposed. The validity of these bounds is demonstrated using an idealized mass-plate model subjected to various shock loads.
INTERNATIONAL JOURNAL OF IMPACT ENGINEERING
(2023)
Article
Engineering, Aerospace
P. V. Kozlov, I. E. Zabelinsky, N. G. Bykova, G. Ya. Gerasimov, V. Yu. Levashov, Yu. V. Tunik
Summary: This paper presents a description of the modernized detonation driven shock tube DDST-M, which simulates the entry of spacecraft into the Earth's atmosphere. The inclusion of a prechamber in the design increases energy efficiency and experiments were conducted to study the radiation characteristics of high temperature air.
Article
Spectroscopy
I. E. Zabelinsky, N. G. Bikova, P. Kozlov, V. Yu Levashov, G. Ya Gerasimov
Summary: The emission spectra of oxygen behind a strong shock wave were studied at different shock wave speeds and pressures, showing that low speeds are dominated by molecular bands and high speeds introduce strong atomic lines. Time oscillograms for typical lines of the spectrum were identified.
JOURNAL OF APPLIED SPECTROSCOPY
(2022)
Article
Physics, Atomic, Molecular & Chemical
M. A. Kotov, P. Kozlov, G. Ya Gerasimov, V. Yu Levashov, A. N. Shemyakin, N. G. Solovyov, M. Yu Yakimov, V. N. Glebov, G. A. Dubrova, A. M. Malyutin
Summary: This study demonstrates the possibility of using a thermoelectric detector to measure the ignition delay time of a combustible mixture. The detector shows high recording capabilities for heat flows, low inertia, high signal-to-noise ratios, and high time resolution. It also allows for a more detailed study of the ignition process of combustible mixtures in shock tubes due to its faster response time.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2022)
Article
Engineering, Aerospace
A. M. Tereza, P. V. Kozlov, G. Ya Gerasimov, V. Yu Levashov, I. E. Zabelinsky, N. G. Bykova
Summary: Ignition delay time measurements were conducted in high-temperature propane-air mixtures behind reflected shock waves at various conditions. The emission characteristics of flammable mixtures associated with electronically excited OH* radical were also recorded. The obtained data were used to improve the understanding of combustion processes in the chambers by analyzing key reactions in different propane-air mixtures.
Article
Engineering, Aerospace
M. A. Kotov, P. V. Kozlov, G. Ya Gerasimov, V. Yu Levashov, A. N. Shemyakin, N. G. Solovyov, M. Yu Yakimov, V. N. Glebov, G. A. Dubrova, A. M. Malyutin
Summary: The problem of flight safety of high-speed aircrafts is primarily related to the reliability of engines, which depends on the understanding of fuel ignition and combustion processes. This study proposes a new method using a thermoelectric detector to register the ignition of shock heated gaseous fuels. The detector demonstrated high efficiency in measuring ignition delay time and showed desirable properties such as high heat flux values, low inertia, high signal-to-noise ratio, and high temporal resolution.
Article
Mechanics
P. V. Kozlov, I. E. Zabelinsky, N. G. Bykova, G. Ya. Gerasimov, V. Yu. Levashov
Summary: This study presents the results of measuring the integral and temporal spectral characteristics of shock-heated air and compares the obtained data with experimental results from other authors.
Article
Mechanics
N. G. Bykova, I. E. Zabelinskii, L. B. Ibraguimova, P. V. Kozlov, V. Yu. Levashov, O. P. Shatalov
Summary: The paper presents experimental data on the emission of pure argon behind the front of a strong shock wave, which can help construct more accurate kinetic models of nonequilibrium ionization and radiation processes.
Article
Mechanics
N. G. Bykova, I. E. Zabelinskii, V. Yu. Levashov, O. P. Shatalov
Summary: This paper analyzes the emission of pure argon behind a strong shock wave, including its velocity range and pressure range. Estimates of electron concentration and population temperature are made using a simplified model, and it is found that the population temperature differs from the gas temperature behind the shock wave.
Article
Physics, Atomic, Molecular & Chemical
P. V. Kozlov, I. E. Zabelinsky, N. G. Bykova, Yu. V. Akimov, V. Yu. Levashov, G. Ya. Gerasimov, A. M. Teresa
Summary: This study presents a technique for calibrating the recording system for gas emission behind the shock wave front at the Shock Tube experimental complex in Moscow State University. It extends the range of data acquisition to the vacuum ultraviolet (VUV) radiation region. The study focuses on obtaining measured values in absolute units and describes a technique for preliminary calibration using standard radiation sources. It shows that the power of radiation in the VUV region can exceed the radiation fluxes from other parts of the spectrum significantly.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2022)
Article
Physics, Fluids & Plasmas
Mikhail A. Kotov, Pavel Kozlov, Gennady Ya Gerasimov, Vladimir Yu Levashov, Andrey N. Shemyakin, Nikolay G. Solovyov, Mikhail Yu Yakimov, Vladislav N. Glebov, Galina A. Dubrova, Andrey M. Malyutin
Summary: A correct understanding of ignition and combustion processes in combustion chambers is crucial for modeling advanced engines and testing combustion kinetic models. Measurement of ignition delay time can provide valuable data for these models, especially at higher temperatures. Thermoelectric detectors offer high time resolution for measuring ignition delay times and recording heat fluxes, allowing for more accurate determination and detailed study of the ignition process.
Article
Physics, Atomic, Molecular & Chemical
P. V. Kozlov, G. Ya. Gerasimov, V. Yu. Levashov, Yu. V. Akimov, I. E. Zabelinskii, N. G. Bykova
Summary: The ignition delay times of propane in propane-oxygen mixtures diluted with argon are measured behind the front of the reflected shock wave in a shock tube. The results show that the ignition delay time of propane increases with an increase in the excess fuel ratio phi in the studied temperature range. Comparing the obtained data with other measurements reveals that at low temperatures (T <= 1000 K), the dependence of the ignition delay time on phi is opposite.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Article
Physics, Atomic, Molecular & Chemical
G. Ya Gerasimov, Yu Tunik, P. Kozlov, V. Yu Levashov, I. E. Zabelinskii, N. G. Bykova
Summary: A new simplified kinetic model of kerosene combustion is developed using n-decane as a substitute, with 24 components and 25 chemical reactions, tested by comparing calculation results with experimental data on ignition delay time in shock tubes.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Article
Physics, Atomic, Molecular & Chemical
P. Kozlov, I. E. Zabelinskii, N. G. Bykova, Yu Akimov, V. Yu Levashov, G. Ya Gerasimov, A. M. Tereza
Summary: The method presented in this study focuses on calibrating the system for recording gas emission behind the front of a shock wave in the range of 190-1100 nm, with an emphasis on obtaining measured values in absolute units. The procedure involves calibrating the measuring system using standard radiation sources and combining panoramic spectrum data with temporal evolution results in a narrow spectral range to accurately determine the radiation power density of plasma components in a shock wave.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Article
Physics, Atomic, Molecular & Chemical
V. Yu. Levashov, P. V. Kozlov, N. G. Bykova, I. E. Zabelinskii
Summary: This study explores the characteristics of radiation shock-heated gases, focusing on the radiation intensity of argon in the initial non-equilibrium emission stage, with discussions on the impact of electrons. Both experimental results and a simplified model are used to analyze the radiation heat fluxes and atomic lines behind the shock wave front.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
